Archive for April 23, 2018

Teardown, Repair & Upgrade of an Agilent 3458A 8.5 Digit Digital Multimeter

In this episode Shahriar repairs and upgrades an Agilent 3458A 8.5 Digit Multimeter. The instrument has been kindly donated by AllTest Instruments Inc. You can access their website here, as well as their eBay store, Bonanza store and TestUnlimited hub. AllTest provides the following:

  • Massive inventory of test and measurement equipment with over 20,000 units to chose from.
  • Full service general laboratory where repairs, refurbishment, and testing are carried out.
  • An additional NIST traceable metrology laboratory with extensive T&M capabilities where OEM grade calibrations are performed.
  • 5% discount on any purchase when The Signal Path Blog is mentioned for first time customers with limit one per customer.

The 3458A unit fails startup conditions with several errors. After close inspection of the boards, the initial problem points to a poorly plugged in fiber-optic cable. After this fix, the unit still fails ACAL on the AC Board. The unit’s NVRAM modules all have to be replaced. During this process the memory of the unit is also upgraded and the firmware is updated to the latest available version. After analysis of the schematics the problem is traced to a damaged JFET input operational amplifier on the attenuator flatness calibrator unit. The replacement allows the unit to pass all self-test and ACAL calibration. The instrument is then NIST calibrated by AllTest Instruments and shows excellent performance when compared with various multimeters in the lab.

Rohde & Schwarz FPC1500 5kHz – 3GHz Spectrum Analyzer Review, Teardown & Experiments

In this episode Shahriar reviews the newly released FPC1500 Spectrum Analyzer from Rohde & Schwarz. With this addition Rohde & Schwarz continues to aggressively target the entry level market across a wide range of instruments. These units are packed with competitive features some of which are not found in other instruments in the same class. The FPC1500 employs a 10.1″ WXGA LCD screes and a built-in tracking generator with a fully independent synthesizer which allows for offset tracking as well as a built-in VSWR bridge capable of making vector S11 measurements. These features combined with built-in WiFi, wide range of measurement capabilities and digital demodulation of ASK/FSK signals provides a competitive product.

This comprehensive review is organized as follows:

00:01:35 – R&S Spectrum Analyzer model overview
00:02:25 – Front and back panel, GUI initial look
00:06:24 – Complete teardown with digital and RF deck analysis
00:19:11 – DUT device overview and specifications
00:20:00 – DUT power on, FPC overload test, single tone, phase-noise and pre-amplifier performance
00:29:41 – TOI measurement capability and multi-tone inter-modulation performance
00:35:07 – Internal source performance, THD measurement, tracking generator and offset-tracking
00:41:55 – Scaler S21 configuration, DUT gain and bandwidth measurement
00:46:08 – DUT Noise-figure measurement and marker functions capability
00:48:57 – DUT variable gain control characterization, AM demodulation, VGA bandwidth and waveform display
00:57:39 – Digital demodulation of FSK/ASK with multilevel frequency shifting, eye-diagram display and analysis
01:01:13 – Vector S11 measurement, web interface, smith chart display and return loss characterization
01:04:45 – Spectrogram measurement, replay mode and trace storage
01:06:55 – Concluding remarks

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